1. Field of the Invention
The present invention relates to a lock-up clutch control apparatus for controlling a engaging force of a lock-up clutch which transmits an output power of an engine to an input axis of the transmission while distributing the output power transmission with a torque converter.
This application is based on Patent Application No. Hei 9-264587 filed in Japan, the content of which is incorporated herein by reference.
2. Background Art
An example of the lock-up clutch control apparatus for transmitting the output power of the engine to the input axis of the transmission while distributing the output power transmission with the torque converter is disclosed in, for example, Japanese Patent Application, First Publication No. Hei 7-332479. Conventionally, this type of lock-up clutch control apparatus is designed such that, during speed shifting of the transmission, the lock-up clutch is turned off (wherein, the engaging force is zero) irrespective of conditions of the clutch before gear-shifting, so that the output of the engine is transmitted to the input axis of the transmission only by the torque converter.
It is preferable to make the lock-up clutch as tight as possible (maximize the engaging force) from the point of view of improving the fuel consumption.
The present invention is directed to the execution of speed shifting while maintaining the lock-up clutch in a tight condition, when the lockup clutch is in a tight condition before the gearshift.
When the gearshift is executed while maintaining the lock-up clutch in a tight condition, it is only necessary to shift the gear ratio. However, when a driver desires to increase a car speed by a down-shift operation, it is preferable to realize a state so as to be able to transmit as possible much amounts of an engine torque to the wheel side after the down-shift operation is completed.
It is therefore the object of the present invention to provide a lock-up clutch control apparatus which enables transmitting a larger amount of torque to the wheel side after the down-shifting operation, in order to improve the fuel economy by reducing fuel consumption by maintaining the lock-up clutch as tightly as possible during the down-shifting operation.